The conventional art for the present invention includes Japanese Laid-Open Patent Application No. 2006-311179 (Patent Document 1), Japanese Laid-Open Patent Application No. 2004-241882 (Patent Document 2), and Japanese Laid-Open Patent Application No. 2000-39862 (Patent Document 3).
Japanese Laid-Open Patent Application No. 2006-311179 proposes detecting color histogram information from color difference signals and detecting average luminance level and luminance histogram information from a luminance signal, thereby controlling the demodulation axes of the color difference signals; and obtaining a video signal of appropriate color saturation in combination with the luminance information. Japanese Laid-Open Patent Application No. 2004-241882 proposes the technique of performing histogram-conversion-type tone correction and color saturation correction in accordance with the luminance distribution of the flesh color part of one frame of a video signal in order to obtain a video of optimum flesh color. Further, Japanese Laid-Open Patent Application No. 2000-39862 proposes the technique of detecting the average luminance level of an input signal and controlling gain with the detected average luminance level, thereby controlling the chroma of a desired hue of the video signal, in order to prevent a decrease in chroma and display a video without dullness at low luminance levels on liquid crystal displays.    Patent Document 1: Japanese Laid-Open Patent Application No. 2006-311179.    Patent Document 2: Japanese Laid-Open Patent Application No. 2004-241882.    Patent Document 3: Japanese Laid-Open Patent Application No. 2000-39862.